1. Field of the Invention
This disclosure relates to an apparatus of modular trip mechanism and auxiliary mechanism in a circuit breaker, such as an air circuit breaker having an overcurrent relay as a controller for detecting a fault current on an electrical power circuit and outputting a trip control signal upon detection of the fault current.
2. Background of the Invention
In low voltage circuit breakers for opening or closing an electrical power circuit having low voltage of several tens to several hundreds volts or automatically tripping a circuit upon detecting an occurrence of a fault current such as overcurrent or short-circuit current on the circuit, a representative of a circuit breaker having a relatively large capacity may be an air circuit breaker. The present disclosure relates to a low voltage circuit breaker with a large capacity.
As such a low voltage circuit breaker with a large capacity, circuit breakers according to the related art provided by the applicant of this disclosure includes a switching mechanism, a trip mechanism, a controller and an auxiliary mechanism.
Here, the switching mechanism, as well known, is a driving mechanism of a movable contact arm to a closing position (so-called ON position) where the movable contact arm contacts a corresponding stationary contact arm, of movable contact arms and stationary contact arms provided for respective multi-phases(multi-poles) electrical power circuits, an opening position where the movable contact arm is separated from the corresponding stationary contact arm (an OFF position as a manually opened position and an automatically open position in response to a fault current detection (so-called trip position). The switching mechanism includes a trip spring, a plurality of links and levers for transferring an elastic driving force of the trip spring to the movable contact arm, latches for maintaining or releasing an elastic energy-charged state of the trip spring, a switching shaft (so-called a main shaft) connected to each of the three-phases circuits for driving the three movable contact arms for the three poles to the closing position or the opening position at the same time.
The trip mechanism is a mechanism for triggering the switching mechanism to a trip position in response to a trip control signal from the controller.
Here, the trip mechanism does not provide a driving force to the switching mechanism to drive to the trip position, but operates to release the latches to output a driving force for a trip operation by releasing the trip spring of the switching mechanism to discharge the charged elastic energy. Thus, the term ‘trigger’ is used.
The trip mechanism includes a coil magnetized by the trip control signal from the controller to generate a magnetic force, a trip bar movable in response to magnetization or demagnetization of the corresponding coil, and the like.
The low voltage circuit breaker with the large capacity may further include an Under Voltage Trip (UVT) mechanism for triggering the switching mechanism to the trip position when a voltage on the electrical power circuit is lowered below a predetermined normal reference voltage, or a shunt trip mechanism for triggering the switching mechanism to the trip position in response to a remote trip control signal from a remote monitoring center.
The controller may be configured as an overcurrent relay (abbreviated as OCR hereinafter), especially, a digital OCR for detecting a fault current on the electrical power circuit and outputting a trip control signal upon detection of the fault current.
The OCR is a device capable of providing and displaying various information, such as simply detecting an occurrence of a fault current on a circuit, outputting a control signal, calculating various status information related to the circuit, calculating a fault-occurred position on the circuit, and the like. The OCR is a control and information monitoring device having a microprocessor and a display capable of processing, calculating and displaying various information.
The auxiliary mechanism includes an Auxiliary Switch (AX) for outputting a signal indicating a closing or opening position, namely, an On or OFF position, of a circuit breaker, and an Alarm Switch (AL) for outputting a signal indicating that the circuit breaker has been tripped.
In the low voltage circuit breaker with the large capacity provided by the applicant of this disclosure, the AX and the AL of the auxiliary mechanism, the trip mechanism, and the under voltage trip mechanism or shunt trip mechanism interlocking with the trip mechanism are arranged dispersedly. This results in requiring a longer time for assembling, testing and producing those components.
Also, in the low voltage circuit breaker with the large capacity, testing for a normal or abnormal operation with respect to each of the AX and the AL of the auxiliary mechanism, the trip mechanism, and the under voltage trip mechanism or shunt trip mechanism should be performed after completely assembling them. Consequently, a long time is required and an entire circuit breaker should be disassembled to find a cause of defect upon occurrence of such defect.